One theory prior to Internet Explorer 8's release was that the new browser would help Microsoft reverse its steadily declining market share by winning back people who had shifted to Mozilla Firefox. Consider it debunked. So far, at least, IE8 doesn't appear to be helping.

Market share for all versions of Internet Explorer continued to fall in March, hitting 66.8 percent, according to data from the Net Applications research firm this week. As ComputerWorld noted, that's the lowest figure for Microsoft's browser since Net Applications began tracking the data. Meanwhile, Firefox continued to climb, rising to more than 22 percent for the month.

Some people are shifting to IE8, as this Net Applications chart shows. But most of that shift is coming from users of previous versions of the Microsoft browser, not from new converts or from people coming back from using Firefox or other browsers.

The new version of Internet Explorer introduced new features and received decent reviews from the Wall Street Journal's Walter Mossberg and others. But others have complained about IE8 being too sluggish. Microsoft had been hoping that IE8 would dispel that reputation, going so far as to release internal speed tests showing the new browser stacking up well against Firefox and Chrome.

The question now: If a full-blown overhaul didn't do the trick for IE's market share, what will?

(Data link via SeattlePI.com's Andrea James.)